This invention relates to the field of synthesis gas generation and more specifically to synthesis gas generation using catalyzed structured packing in reformer tubes in a combustion fired reformer.
The steam reforming process is a well known chemical process for hydrocarbon reforming. A reactant gas mixture comprising steam and a light hydrocarbon reacts in the presence of a catalyst to form hydrogen, carbon monoxide and carbon dioxide. Since the reforming reaction is strongly endothermic, heat must be supplied to the reactant mixture, such as by heating catalyst-containing tubes in a furnace called a reformer. The amount of reforming, i.e. conversion, achieved depends, among other things, on the temperature of the gas leaving the catalyst-containing tubes. Exit temperatures in the range 700-950° C. are typical for conventional steam-hydrocarbon reforming.
The light hydrocarbon feedstock forming the reactant gas mixture is typically pretreated to remove sulfur, and to saturate olefins. The light hydrocarbon feedstock may be mixed with steam and prereformed so that hydrocarbons heavier than methane react with steam to form a mixture having substantially reduced concentrations of the heavier hydrocarbons, and enriched in hydrogen.
Conventionally, reforming catalyst is in the form of pellets, typically comprising nickel dispersed on a suitable ceramic support, such as alumina. The pellets are contained in several tall vertical reformer tubes, generally 5 cm to 20 cm in diameter.
Reformer tubes are spaced inside the furnace for receiving heat from flames generated by surrounding burners fired with fuel and an oxygen-containing gas, such as air or the exhaust from a gas turbine. Radiation from the combustion flames heats the reformer tubes and the gases flowing therein, providing the heat of reaction for reforming the light hydrocarbon and steam. It is desirable to provide sufficient heat transfer to provide heat for reforming.
The reformer tubes and the catalyst contained therein represent one of the most expensive parts, if not the most expensive part of the reformer. Therefore it is desirable to reduce the number of reformer tubes required to process a given amount of reactant gas mixture. Alternatively, it is desirable to process an increased amount of reactant gas mixture for a given number of reformer tubes.
The reformer tubes generally last longer than the catalyst remains sufficiently active. It is therefore desirable that the catalyst is easily replaced. Obviously costs are increased if both the reformer tubes and the catalyst need to be replaced compared to only replacing the catalyst.
Reactors containing catalyzed structured packing have been described, for example tubular reactors used in reforming. The use of a structured packing in a steam reformer has been disclosed, for example in co-pending patent application Ser. No. 11/435541 and U.S. Pat. No. 4,340,501 to Davidson. Compared to dumped packing, also called random packing, such as catalyst pellets, structured packing can produce a lower pressure drop, is not easily fluidized, and is not prone to settling or crushing. It is desired to provide effective operating parameters for tubular reactors containing catalyzed structure packing.
Often, advantage is taken of the lower flow resistance of structured packing by using less compression, resulting in power savings for the process.